1. Field of the Invention
The present invention relates to a display unit and, more particularly, to a technique for guiding the sight line of a driver.
2. Description of the Related Art
Head-up display devices mounted on vehicles are typically configured such that display light emitted from a projection unit is projected onto an optical member (half mirror) called a combiner; and light reflected off a surface of the combiner is reflected in a viewing direction of the driver and guided to a predetermined eye point as a viewing position of the driver (see, for example, Japanese Patent Application Laid-open No. 2006-11122). The combiner is disposed at a position in front of the driver's seat, for example, above the instrument panel, that is easily visually recognizable by the driver. A front windshield, instead of the combiner, may be used as the surface for reflecting the display light.
The head-up display device forms a display image as a virtual image at a position anterior to the combiner in the vehicle forward direction (that is, posterior in the viewing direction). This offers an advantage that the driver requires early small focus adjustment for visually reeconizing the display image. In addition, the head-up display device allows the driver to visually recognize the display image anterior to the combiner in the vehicle forward direction superimposed on a view anterior to the vehicle that is visually recognized through the combiner. The head-up display device can thus present information in a novel mode different from display using an ordinary display panel.
Such a head-up display device can be used for, for example, displaying the vehicle traveling speed. The head-up display device is therefore suitable for displaying highly important information such as vehicle speed, because the driver can visually recognize the speed display with his/her head up and without involving any considerable movement of the sight line or focus adjustment.
The combiner of the head-up display device can display various types of information, but it is not very often that the combiner presents a large amount of information at once. For example, if a malfunction or any other fault occurs in the vehicle, it is often the case that only a warning display containing a symbol such as an exclamation mark (!) is displayed; and a message describing the detail of the fault is not displayed. This is to prevent the field of view of the driver from being interrupted or to prevent the driver from being distracted from the forward view, thereby preventing proper driving by the driver from being hindered.
When a fault occurs, therefore, a message or the like that describes the detail of the fault may be displayed on another display such as a meter unit, in addition to the warning display displayed on the combiner. The combiner and such another display as a meter unit are, however, generally spaced apart from each other in the vertical and horizontal directions (that is, directions perpendicular to the viewing direction). As a result, the driver can fail to notice that such another display as a meter unit displays information for describing the detail of the fault.
In addition, whereas such another display as a meter unit displays information on its display surface, the virtual image displayed by the head-up display device is formed posterior to the combiner in the viewing direction to be visually recognized by the driver. In other words, the image forming position of the display image by the head-up display device is spaced apart in the viewing direction from the display screen of such another display as a meter unit. Here again, the driver can fail to notice that such another display as a meter unit displays information for describing the details of the fault.
To allow the driver to visually recognize such another display as a meter unit while he/she is paying attention to the combiner, the sight line has to be guided from the combiner to such another display as a meter unit.
The present invention has been made in view of the above-described circumstance, and it is an object of the present invention to provide a display unit capable of guiding the sight line of a driver.